SEVENTY-FIVE years ago, Herbert Hoover was in the White House, Amelia Earhart was in the air – and tickets to the first Radio City Music Hall Christmas Spectacular were 75 cents.

Time marches on. That top ticket is now $100, but “The March of the Wooden Soldiers” and “The Living Nativity” remain the same. And therein lies their charm.

Presidents come and go, styles change, but the Rockettes keep kicking. So when the big red curtain goes up on Nov. 9, expect the 75th Spectacular to feature all the same crowd-pleasers, with a few more bells and whistles.

“There’s always been a reference to doing a major Busby Berkeley moment,” concedes executive producer John Bonani. “I’ve also had suggestions about making the show a straight play, or partnering the Rockettes with men in top hats and tails.”

Not gonna happen.

Still, those who’ve seen the show before – and 60 percent of the hall’s ticket buyers hail from the tri-state area, including 81-year-old Adam Medway of Basking Ridge, N.J., who’s seen it every year since he was 6 – may note several new costumes and five new scenes, including a filmed retrospective about the history of the hall and the Rockettes.

There’s also a number set atop a two-story bus – and snow that will fall over the house.

As for the Rockettes – well, they get taller and stronger every year. And more diverse.

In the ’40s, when Viola Varble was on the line, conformity was key – so much so, she says, that when the dancers went on vacation, troupe founder Russell Markert would warn them: “If you get a tan, we’ll have to do something about it.”

These days, there are Asian- and African-American Rockettes, and competition has never been stiffer.

This year’s audition drew more than 400, says choreographer/director Linda Haberman. Only two made it to Radio City.

And aside from dancing, standards are tough. Those under 18 – or under 5-foot-6 or over 5-foot-10½ – need not apply.

“Most people don’t realize that we really have to execute everything the exact same way for 200 shows a season,” says Rockette dance captain Karen Keeler.

“If your arm is supposed to be 90 degrees, then every single time it has to be that way… We teach every shoulder angle, every elbow angle – we even get into where your cheek and eye focus should be.”

And then there’s the little matter of navigating the onstage grid, and counting the steps to stay in formation even when things go awry. And they do go awry.

“A headpiece might go flying or the scenery doesn’t work,” Keeler says. “That’s part of live theater and you run with it.”

One year, a reindeer was added to the show’s menagerie (three camels, two donkeys and seven sheep), but the hall ran into “an antler-maintenance problem”: i.e., its antlers fell off.

An ex-Rockette remembers the time a handler got a … rise from a donkey.

“The donkey’s nuzzling her and I’m whispering, look at that donkey!” she recalls. “Hey, when you’re doing five shows a day, you need something to get you through!”

But most Rockettes say the show is its own reward.

“When the curtain goes up and you’re out there dancing,” says Varble, now 84, “you feel you’re the luckiest girl in the world.”

HIGH-STEPPIN’ HIGHLIGHTS

1932: Radio City Music Hall opens its doors two days after Christmas with The “Roxyettes” – all 36 of them.

1933: The first “Christmas Spectacular” appears during a screening of “Flying Down to Rio,” with three elements that have yet to change: the March of the Wooden Soldiers, the Living Nativity and “the Roxyettes.”

1934: Enter the Rockettes – same troupe, new name.

1942-45: Touring groups of the Rockettes entertain the troops during WWII.

1944: The Lippizaner Stallions team with the Rockettes for screenings of “National Velvet.”

1948: The hall turns into a virtual circus – with live bears, a ballet company dressed as tigers and the Rockettes doing a number called “Puttin’ on the Dog.” Wielding the baton is Anton Coppola, Francis Ford’s dad.

1957: Amid its balloons and floats, the Macy’s Thanksgiving Day Parade inserts … the Rockettes.

1961: Martha Graham Dancers and the Flying Wallendas share the bill with the Rockettes.

1978: “Caravans” pulls in for Radio City’s final Christmas film and live show combo. The hall itself is slated for demolition, and the Rockettes kick up a fuss to save it.

1979: Designated a New York landmark, the hall is spared from the wrecking ball. The “Radio City Christmas Spectacular” expands into a 90-minute, stand-alone show.

1988: The first African-American Rockette joins the line; 150 million couch potatoes watch the troupe perform at the Super Bowl halftime show.

1994: The show hits the road, starting with a holiday run in Branson, Mo. After that, touring versions play a handful of different cities each year, but nothing’s bigger than the show in New York.

2001: The Rockettes dance at President George W. Bush’s inauguration.

2006: New costumes, an LED screen and Linda Haberman, the first female director and choreographer.

2007: The 75th year of “The Christmas Spectacular,” which will play in eight cities across America, including New York. And the March of the Wooden Soldiers marches on …